1. Field of Invention
The invention relates generally to mastitis detection and more particularly to a novel fool proof on-site mastitis detector for use in mechanized milking operations.
2. Prior Art
Mastitis is a disease of the udder, which infects milk animals such as cows, sheep, and goats and causes serious losses of milk production, the disease can also be terminal. Early detection is significant in effectuating an early cure to avoid permanent injury to the udder. Heretofore, it has been the practice of dairy farmers to send milk samples from time to time to distant laboratories for analysis to determine whether or not any cow has mastitis. This is expensive and time consuming, especially where each cow of a herd needs to be tested.
Once mastitis is advanced in a given cow, the injury to the udder is permanent as the spongy cells of the udder where the milk accumulates do not regenerate once disabled by mastitis. Many changes in the characteristics of milk occur when mastitis infects a milk animal, e.g. the chloride content of the milk, its pH, its conductivity, its opacity, its viscosity, and so on. One of the most pronounced changes in the presence in the milk of solid white particles or curdles. The cost of equipment to measure these various parameters varies widely, as does their durability, the difficulty of keeping the working parts clean and sterile, the difficulty of comprehending the indication presented, and the lack of suitability for use on-site in the farm milking operation.
Heretofore most mastitis screening has been done by periodically sending samples to a laboratory. There have however been some proposals for on-site detection. There are disclosed in U.S. Pat. Nos. 3,695,230; 3,664,306; 3,762,371 and 3,968,774. Each can be used during milking in an attempt to determine the presence of mastitis by comparing the conductivity of milk from different quarters of an udder, using an electrical bridge. Comparing resistance presents several problem.
For example, inaccurate results will be obtained if ineffective cleaning leaves coatings of fat or milk stains on the electrodes of conductivity cells forming part of the comparison apparatus. Uniting the electrodes to the surrounding molding without leaving crevices in which bacteria and solid deposits can lodge is difficult and tends to make conductivity cells with electrodes which contact the milk fairly expensive.
A further problem arises in taking conductivity measurements while the liquid flows continually through the apparatus. An additional problem associated with reliance upon measurements of change in conductivity to detect mastitis is that many other factors cause changes in conductivity, including diet, condition of the animal, season of the year, temperature of the milk, and so on.
In addition to these other problems, conductivity measuring devices have several other inherent disadvantages. They require segregation of the milk from each section of the udder of each cow until the testing process is complete. They require complicated and expensive electrical circuitry using a minimum of eight electrodes in each device. These devices also necessarily bring four currents of electricity into direct contact with the stream of milk coming from the teats, allowing the possibility of electrical shock to the animal.